Electromagnetic and Calometric Absolute Measurements. 127 



of a gas regulate their motions so as to move in a particular manner, 

 though we doubt whether, if we had not arrived at this conclusion 

 independently for ourselves, we should have been able to make a 

 practical application of it. The point it has been our object to call 

 attention to (and which apparently has not been noticed by others) 

 is, that the motion of the particles of a gas within the range of free 

 path precisely satisfies all the conditions Le Sage arbitrarily assumed 

 in order to produce gravity — or that the special character of the 

 motion Le Sage arbitrarily assumed his streams of particles to have, 

 actually exists within the range of free path of the particles of a gas 

 — in other words, that all the effects of gravity can be produced by 

 the mere existence of a gas in space, and indeed must be produced if 

 such a gas exists. 



XVIII. Electromagnetic and Calometric Absolute Measurements: 

 the Absolute Value of Siemens 3 s Unit of Resistance in Electro- 

 magnetic Measure ; the Relation between the Current-ivork 

 and the Heat-evolution in stationary Galvanic Currents ; and 

 the Absolute Values of some constant Hydroelectromotive 

 Forces in Electromagnetic Measure. ( Condensed Comparison 

 of the Results of a Series of Investigations.) By H. F. 

 Weber, Professor of Mathematical and Technical Physics 

 at the Federal Polytechnic Academy of Zurich. 



[Continued from p. 43.] 



III. The Heat produced by Stationary Galvanic Currents. 



MR. JOULE, thirty-seven years since, showed by experi- 

 ment that the quantity of heat which a stationary gal- 

 vanic current of intensity i generates in a conductor whose 

 resistance is w, during the time z, is proportional to i 2 wz. Sir 

 W. Thomson then, in 1851 (and Prof. Clausius and others 

 later), proved in the theoretical way that the value of the me- 

 chanical work which is expended in the stationary galvanic 

 current of the intensity i, in a conductor with the resistance w, 

 along which the electromotive force E is in action, in the time 

 z is equal to the product iEz, or, pursuant to Ohm's law, equal 

 to the expression i 2 wz, where the quantities E, i, io are to be 

 taken as measured according to absolute measure. If we 

 make the assumption that, in a stationary galvanic current in 

 which the evolution of heat is the only action of the current- 

 flow, the amount of heat developed in the unit of time, Q, is 

 the full equivalent of the work expended in the same time, 

 then we have 



JG=^=zE, 



where J denotes the mechanical equivalent of the unit of heat. 



